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          <th colspan="3" align="center">Opening a Transactional Environment and
            <span xmlns="http://www.w3.org/1999/xhtml">Database</span>
            
            
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            <h2 class="title" style="clear: both"><a id="envopen"></a>Opening a Transactional Environment and
            <span>Database</span>
            
            
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      <p>
            To enable transactions for your environment, you must initialize the
            transactional subsystem. Note that doing this also initializes the
            logging subsystem. In addition, you must initialize the memory pool
            (in-memory cache). You must also initialize the locking subsystem.  
            
            
            <span>
                For example:
            </span>
            
        </p>
      <pre class="programlisting">#include "db_cxx.h"

...

int main(void)
{
    u_int32_t env_flags = DB_CREATE     |  // If the environment does not
                                           // exist, create it.
                          DB_INIT_LOCK  |  // Initialize locking
                          DB_INIT_LOG   |  // Initialize logging
                          DB_INIT_MPOOL |  // Initialize the cache
                          DB_INIT_TXN;     // Initialize transactions

    std::string envHome("/export1/testEnv");
    DbEnv myEnv(0);

    try {

        myEnv.open(envHome.c_str(), env_flags, 0);

    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error opening database environment: "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
        return (EXIT_FAILURE);
    }

    try {
        myEnv.close(0);
    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error closing database environment: "
                &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
        return (EXIT_FAILURE);
    }

    return (EXIT_SUCCESS);
} </pre>
      <p>
        You then create and open your database(s) as you would for a non-transactional system.
        <span>
            The only difference is that you must pass the environment handle to
            the 
                
                <span>
                    <code class="methodname">DbEnv::open()</code> method,
                </span>
             and you must open the database within a transaction.
             Typically auto commit is used for this purpose. To do so, pass 
            <code class="literal">DB_AUTO_COMMIT</code> to the database open command.
            It is recommended that you close all your databases before you close 
            your environment.
            For example:
        </span>

        
    </p>
      <pre class="programlisting">#include "db_cxx.h"

...

int main(void)
{
    u_int32_t env_flags = DB_CREATE     |  // If the environment does not
                                           // exist, create it.
                          DB_INIT_LOCK  |  // Initialize locking
                          DB_INIT_LOG   |  // Initialize logging
                          DB_INIT_MPOOL |  // Initialize the cache
                          DB_INIT_TXN;     // Initialize transactions

    <strong class="userinput"><code>u_int32_t db_flags = DB_CREATE | DB_AUTO_COMMIT;
    Db *dbp = NULL;
    const char *file_name = "mydb.db";</code></strong>

    std::string envHome("/export1/testEnv");
    DbEnv myEnv(0);

    try {

        myEnv.open(envHome.c_str(), env_flags, 0);
        <strong class="userinput"><code>dbp = new Db(&amp;myEnv, 0);
        dbp-&gt;open(NULL,       // Txn pointer 
                  file_name,  // File name 
                  NULL,       // Logical db name 
                  DB_BTREE,   // Database type (using btree) 
                  db_flags,   // Open flags 
                  0);         // File mode. Using defaults </code></strong>

    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error opening database and environment: "
                  &lt;&lt; file_name &lt;&lt; ", "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
    }

    try {
        <strong class="userinput"><code>dbp-&gt;close(0);</code></strong>
        myEnv.close(0);
    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error closing database and environment: "
                  &lt;&lt; file_name &lt;&lt; ", "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
        return (EXIT_FAILURE);
    }

    return (EXIT_SUCCESS);
} </pre>
      <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
        <h3 class="title">Note</h3>
        <p>
                Never close a database  that has active transactions. Make sure
            all transactions are resolved (either committed or aborted)
            before closing the database.
        </p>
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